Washington and Oregon are among only four states to have recently legalized recreational marijuana, a legal change unprecedented in the U.S. and worldwide. Debate exists about the potential positive and negative impacts of legalization, but there is agreement that certain potential negative consequences of legalization should be mitigated, including youth use, drug dependency, and impaired driving. In response to state legalization of recreational marijuana, some communities are initiating additional marijuana regulatory policies or taxes. Currently, there is no evidence base to predict the effectiveness of such local policy actions for moderating the potential negative consequences of marijuana legalization, or how these policies are related to other public health and social outcomes (e.g., injuries, crime, tax revenue). Furthermore, it is unclear how different state tax structures may influence properties of the recreational market (e.g., THC potency of products), which could in turn influence public health and social outcomes of legalization. The Aims of the proposed study are to: (1) Describe implementation of local (city or county) policies to regulate medical o recreational marijuana (e.g., zoning ordinances, taxes) and association with retailer density; (2) Assess activities of the recreational marijuana market (e.g., product, price and potency), and whether different state tax bases are associated with different product potency; and (3) Assess whether city or county-level marijuana policies (e.g., local zoning restrictions or taxes) mitigate key potential negative impacts of marijuana legalization (i.e., youth marijuana use, impaired driving, drug dependence, emergency department visits, hospitalizations), and whether they are associated with other public health and social outcomes (i.e., adult marijuana use, arrests, other substance use, educational outcomes, tax revenues). We will collect and review local marijuana policies across communities in both states, and use an interrupted time series design to assess the association between local policies and behavioral, public health and social outcomes. We will rely on multiple established public health surveillance and other data reporting mechanisms associated with behavioral surveillance, health, safety, treatment and crime systems, which are largely common across both states. Additionally, we will analyze transaction-level data from the new marijuana markets to describe community-level market and consumer behaviors as well as revenue. Findings from this study will provide policymakers and other stakeholders with understanding of how legalization is being implemented, and strong evidence about the effectiveness of local policy actions for mitigating negative impacts.